I forgot about PCMag’s review of a number of these services earlier today. Curiously they miss RawSugar and Furl, slam del.icio.us (which misses the strength of community point I made earlier), and mistakenly say you need Yahoo!’s toolbar to use MyWeb (incorrect – they have bookmarklets like everyone else!). via Jeremy Zawodny.
Update: Wikipedia has a page covering social bookmarking that I could have linked to yesterday to save myself some time. Check it out for a great list of related services.